The present invention relates to resistors adapted for use in electrical circuits and formed of aluminum-titanium alloys.
Heavy duty power resistors are commonly employed in electrical circuits to control electrical current flow by converting electrical energy to heat, which may then be dissipated into the surrounding environment. Normally, resistors rated at 300 watts and above are considered power resistors. Typically, power resistors have been made from nickel-chromium alloys (NiChromes), copper-nickel alloys (Cuxe2x80x94Ni) or stainless steel alloys, with FeCrAl, 304 and 430 being the most common stainless steel types. Stainless steel is often modified with additional metals to improve its electrical characteristics, for example, resistivity and changes in resistivity levels over an operating temperature range. While all of these materials may be used in high temperature applications, i.e. up to about 1000xc2x0 C., they all have one or more shortcomings which compromise their use.
For example, the nickel-chromium alloys commonly referred to NiChrome materials are expensive and heavy, both of which factors limit their use in a wide range of applications. On the other hand, the copper-nickel alloys are expensive and exhibit relatively low working temperatures and melting points. Additionally, the copper-nickel alloys are disadvantageous in that they are not readily available in sheet form. The stainless steel alloys also exhibit a relatively low resistivity and typically the resistivities of these alloys vary substantially over a temperature range, thereby rendering the alloys unsuitable for applications requiring precise resistivity requirements. Additionally, the type 430 stainless steel which is commonly employed is slightly magnetic and therefore unsuitable for low inductance applications. Various modified forms of stainless steel are also slightly magnetic and therefore unsuitable for low inductance applications. These modified stainless steel alloys are also typically more expensive and therefore not attractive for widespread use.
Accordingly, there is a continuing need for new resistors which would be suitable for widespread use, and particularly in heavy duty environments.
Accordingly, it is an object of the present invention to provide new resistors which may be advantageously employed in various applications owing to a desirable combination of properties. It is a further object of the invention to provide non-magnetic and lightweight resistors. It is a related object to provide such resistors which can be rated at 10 watts and above and which may be employed in heavy duty power environments. It is another object to provide resistors which may be employed in high temperature applications and in a temperature range of xe2x88x9240 to 1200xc2x0 C.
These and additional objects are satisfied by the present invention which is directed to resistors adapted for use in electrical circuits. The resistors are formed of an alloy comprising from about 50 to 95 mol percent aluminum, from about 5 to about 50 mol percent titanium and up to about 15 mol percent of at least one additional metal or boron or a combination thereof. The resistors according to the present invention are strong, lightweight and non-magnetic. Additionally, the resistors according to the present invention exhibit nearly constant resistivity over a wide operating temperature range. The alloys from which the resistors are formed exhibit a good combination of ductility, material density and melting point to allow efficient manufacture of the resistors.
These and additional objects and advantages provided by the present invention will be more fully understood in view of the following detailed description.